Avalanche forecast

Northwest Coastal

Dec 9 – 10, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
1 · Low
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Highlights

The Danger Ratings are based on precipitation amounts forecast for the southern portion of the region.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    New snow combined with forecasted strong northwesterly winds will have created windslabs in the lee of terrain features. Strong winds often create slabs further down the slope than expected and in open areas below treeline.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–6
    Deeply buried facet/crust weaknesses are prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. They may be difficult to trigger, but deep persistent slab avalanches are often very large and destructive.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Monday: Moderate precipitation with westerly and southwesterly winds 30-50km/h gusting to 90km/h. Freezing levels expected at 600m with alpine temperatures -5 degrees.Tuesday: Light to locally moderate precipitation, temperatures cooling to -7 in the alpine. Winds southwesterly moderate to strong.Wednesday: Light flurries, winds light from the northwest and alpine temperatures -6.

Avalanche Summary

Natural activity isolated to the storm snow to size 1.5. Explosives testing in the past few days north of the Stewart region indicate an avalanche running to size 3.5 in north facing alpine terrain failing in a weak layer of facets near the base of the snowpack.

Snowpack Summary

An additional 15-30cm of snow has fallen accompanied by strong winds. This sits on top of the settled storm accumulations from last week. Alpine and treeline surface snow conditions are variable with buried wind slabs, newly formed wind slabs and areas that are heavily scoured. The mid-pack is gaining strength and is well settled.A November facet/crust layer can be found near the base of the snowpack. We don not have much recent information on this facet/crust interface, so it may be worth digging down yourself to test its reactivity.Total snowpack depth above 1000 m is 160-220 cm deep. Below 1000 m the snowpack shows a sharp transition from 100 cm dropping to 50 cm, and is generally below threshold.

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